SpringMVC拦截器——实现登录验证拦截器的示例代码

本例实现登陆时的验证拦截，采用SpringMVC拦截器来实现

当用户点击到网站主页时要进行拦截，用户登录了才能进入网站主页，否则进入登陆页面

核心代码

首先是index.jsp,显示链接

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
  <base href="<%=basePath%>" rel="external nofollow" >

  <title>首页</title>
  <meta http-equiv="pragma" content="no-cache">
  <meta http-equiv="cache-control" content="no-cache">
  <meta http-equiv="expires" content="0">
  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
  <meta http-equiv="description" content="This is my page">
  <!--
  <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" >
  -->
 </head>

 <body>
   <div style="margin:0 auto;padding-top:100px;font-size:18px;" align="center">
     <p><a href="loginpage.html" rel="external nofollow" >登陆</a></p>
     <p><a href="user/home.html" rel="external nofollow" >用户中心</a></p>
     <p><a href="exception.html" rel="external nofollow" >触发异常</a></p>
   </div>
 </body>
</html>

controller类

package com.jikexueyuan.demo.springmvc.lesson4.controller;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.jikexueyuan.demo.springmvc.lesson4.constant.Global;
import com.jikexueyuan.demo.springmvc.lesson4.exception.MyException;
import com.jikexueyuan.demo.springmvc.lesson4.model.User;
import com.jikexueyuan.demo.springmvc.lesson4.service.LoginService;

/**
 * 这个例子讲解了如何定义MVC三层注解，使用@Resource进行注入，以及使用@RequestMapping、@RequestParam 、@SessionAttributes
 */

@Controller
public class LoginController extends BaseController {

  @Resource
  LoginService service;

  @Resource
  HttpServletRequest request;

  @RequestMapping("/exception")
  public void exception() throws MyException{
    throw new MyException("测试springmvc中的异常捕获");
  }

  @RequestMapping("/loginpage")
  public String toLoginPage(){
    return "/WEB-INF/jsp/login.jsp";
  }

  @RequestMapping("/user/home")
  public String toUserHome(){
    return "/WEB-INF/jsp/userhome.jsp";
  }

  @RequestMapping("/logout")
  public String logout(){
    request.getSession().removeAttribute(Global.USER_SESSION_KEY);
    return "redirect:/";
  }

  @RequestMapping(value = "/doLogin", method = RequestMethod.POST)
  public String doLogin(@RequestParam String userName, @RequestParam String password){

    try {
      User user = service.doLogin(userName, password);
      request.getSession().setAttribute(Global.USER_SESSION_KEY, user);
      return "redirect:/user/home.html";
    } catch (Exception e) {
      return "/WEB-INF/jsp/login.jsp";
    }

  }

}

当点击用户中心时，触发拦截，相关配置如下

在spring-mvc.xml中加上拦截配置，拦截所有URL中包含/user/的请求，当然请求用户中心时就会触发这个拦截器了

<mvc:interceptors>
    <mvc:interceptor>
      <!-- 拦截所有URL中包含/user/的请求 -->
      <mvc:mapping path="/user/**"/>
      <bean class="com.jikexueyuan.demo.springmvc.lesson4.interceptor.LoginInterceptor"></bean>
    </mvc:interceptor>
  </mvc:interceptors>

然后是bean指向的具体的interceptor类，如果session保存的用户信息为null，则跳到login页面，postHandle和afterCompletion方法都不执行，反之都执行。

package com.jikexueyuan.demo.springmvc.lesson4.interceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import com.jikexueyuan.demo.springmvc.lesson4.constant.Global;

public class LoginInterceptor implements HandlerInterceptor {

  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    Object user = request.getSession().getAttribute(Global.USER_SESSION_KEY);
    if (user == null) {
      System.out.println("尚未登录，调到登录页面");
      response.sendRedirect("/loginpage.html");
      return false;
    }

    return true;
  }

  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    System.out.println("postHandle");
  }

  @Override
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    System.out.println("afterCompletion");
  }

}

至此，简单的springmvc拦截器就完成了。

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